Position-measuring devices are required in a wide variety of technical fields in order to determine the position (length and/or angle) of movable components in systems and machines. Based on their functional principle, position-measuring devices of this type are subdivided into two groups. There are, for example, incremental position-measuring devices, in which the position is determined by counting graduation periods of an incremental graduation. There are also absolute position-measuring devices, in which the position is obtained by scanning and analyzing an absolute graduation.
In contrast to absolute position-measuring devices, incremental position-measuring devices have a simple, robust design, but the drawback that no positional information is available directly following the switch-on operation, and it is necessary to first cross a reference mark in a so-called reference run before the absolute position can be inferred. For this reason, absolute position-measuring devices, in which an absolute position value is available at all times, also immediately after the device is switched on, have since become the preferred choice in many technical fields. An absolute position-measuring device is described, for example, in European Published Patent Application No. 0 660 209.
A technical field in which the use of absolute position-measuring devices continues to be problematic concerns systems or machines that are exposed to ionizing high-energy radiation, or whose application field requires the use of such radiation. Especially the field of medical technology should be mentioned in this context, where ionizing high-energy radiation is selectively used to treat diseases or to delay their progression. Gamma radiation, X-ray radiation or particle radiation (protons, neutrons, electrons etc.) are predominantly used in this regard.
Incremental position-measuring devices that are exposed to such radiation exhibit a fairly robust response due to their simple design. On the other hand, absolute position-measuring devices, which require a more complex design to determine an absolute positional value, tend to fail when exposed to ionizing, high-energy radiation. Memory components are especially problematic, since memory content may change under the influence of radiation. The failures caused by this problem are frequently difficult to understand because of the inconsistent error images they create.
German Published Patent Application No. 10 2012 218 890 describes an absolute position-measuring device, which may be suitable for use in an environment in which it may be exposed to ionizing high-energy radiation. It includes two subassemblies, in which a first subassembly includes functional blocks used directly for a position measurement, and a second subassembly including functional blocks that perform auxiliary and supplementary functions. The first subassembly is completely made up of so-called radiation-hardened components, e.g., components that are suitable for use in a radiation region of a machine. Because the second subassembly can be situated in a separate location from the first subassembly and thus outside the radiation region of the machine, the second subassembly may be made up of conventional components. This separation of the functions of the position-measuring device provides a favorable cost/benefit ratio.
This also applies to the service case, because the exchange of one of the subassemblies may possibly be sufficient. In practice, the subassembly to be exchanged will frequently involve the first subassembly, not only because it is operated in the environment of ionizing high-energy radiation, but also because this subassembly is exposed to mechanical wear, temperature fluctuations, etc.
The manufacturer frequently assigns data to the first subassembly that are required for operating the position-measuring device. The data may involve information regarding the technical specifications (resolution, interface protocol, type designation, etc.), which are also referred to as electronic nameplates. In addition, these data may include calibration values required to optimize the accuracy of the position-measuring device. Since the use of memory components is problematic for the aforementioned reasons, the manufacturer of the position-measuring device or the first subassembly must supply these data separately from the device, e.g., stored on a data carrier (DVD-ROM, CD-ROM, etc.) or in the form of a hard copy.
A service technician handling the exchange of the first subassembly must then also copy the supplied data to the location where they are required for operating the position-measuring device, e.g., either into the second subassembly (where memory chips may be used because it is operated outside the radiation region of the machine), or into the sequential electronics to which the position-measuring device is connected (e.g., a numerical control). However, this procedure is undesired because it is complicated and prone to errors.